In agricultural operations and especially on dairy farms, a herd of milk cows will produce very substantial amounts of manure during the winter season when, for most of the time, they are indoors, and this manure is a valuable product to be spread upon the farm, especially in the spring or even during the winter months by means of a manure spreader which, in general, is mobile and pulled by a tractor from which power to drive the spreader is derived by a rear p.t.o. of well known type for purposes of driving an endless apron which extends along the bed of the body of the manure spreader, as well as a transversely disposed rotary distributor at the discharge end of the body which engages and flings the mass of manure gradually fed thereto by rearward movement of the upper span of the endless apron.
Depending upon how the mass of manure is located in the body of the spreader, it is preferable to provide a variable drive for the apron so that, for example, if the mass is greater at one location in the body of the spreader, it is preferable to drive the apron at a slower rate and then possibly increase the speed as masses of lesser amount are encountered during the entire unloading of the spreader. This is because, in general, a rotary distributor usually is driven at a relatively constant speed. Also, and more importantly from the standpoint of the present invention, when a load of manure nears the end of being discharged, it is customary to stop the operation of the distributor but move the apron in discharge direction sufficiently to more or less completely unload the entire mass of the manure while this relatively small last portion of the load is not interfered with by the distributor which, because of its normal rotary direction is capable of picking up some of the manure and flinging it back into the body of the spreader.
While the normal relatively slow and fast operation of the apron is fully adequate to effectively unload the spreader in conjunction with the distributor, it now has become desirable to effect the last cleanout operation at a still faster speed than normal fast speed of the apron so as to expedite the entire discharge from the spreader, especially while the distributor is idle. Means to arrange for the faster drive of the apron during the final cleanout operation is the object of the present invention and the means for accomplishing this are set forth in detail hereinafter.
The desire to effect a fast cleanout of a manure spreader has been the object of prior developments and constitute improvements, for example, over the type of operation of a manure spreader such as is the subject matter of prior U.S. Pat. No. 3,722,307 to Campbell, dated Mar. 27, 1973, in which clutches are operated to provide, for example, relatively slow and fast operation of the apron without having any provision for a more rapid cleanout drive as is now desired. However, the Campbell patent does include mechanism for idling the distributor when desired, such as during the final cleanout operation when, for example, the apron may be driven at the normal fast speed.
The aforementioned improvements over the structure of the Campbell patent are illustrated, for example, in prior U.S. Pat. No. 2,953,386 to McCarty, dated Sept. 20, 1960, in which ratchet mechanism is provided for producing a faster drive speed of the apron during the cleanout operation than the normal fast operation of the apron. The invention covered by said patent is owned by the assignee of the instant invention and it has been found that the structure illustrated in the patent has certain fallacies which are undesirable and the present invention constitutes an improvement thereover.
Still another type of manure spreader in which a fast cleanout speed is effected comprises the subject matter of prior U.S. Pat. No. 4,196,859 to Trott et al, dated Apr. 8, 1980 in which the drive mechanism is at the forward end of the body of the manure spreader and a pair of long drive shafts are required to extend along one side of the body respectively for actuation of the apron and the distributor. This mechanism necessitates the use of a variable speed pulley assembly in which a cam-operated shifter assembly is required with respect to a jaw clutch and said variable speed pulley assembly. The present invention is submitted to be an improvement over the aforementioned prior examples of rapid cleanout mechanism, details of which are set forth below.